\begin{tikzpicture}[>=Stealth,
    every node/.style={fill=white, inner sep=1pt},
    scale=0.7,
]
    \pgfmathsetmacro{\a}{8}
    \pgfmathsetmacro{\b}{6}
    \pgfmathsetmacro{\c}{1.5}

    \draw [ultra thick] (0, 0) rectangle (\a, \b);

    \draw [ultra thick] (0, 0) rectangle (\c, \c);
    \draw [ultra thick] (\a - \c, 0) rectangle (\a, \c);
    \draw [ultra thick] (0, \b - \c) rectangle (\c, \b);
    \draw [ultra thick] (\a - \c, \b - \c) rectangle (\a, \b);

    \draw [dashed] (\c, \c) rectangle (\a - \c, \b - \c);

    \draw [<->] (0, \b+0.5) to [xianduan={below=0.5cm}] node {$80$} (\a, \b+0.5);
    \draw [<->] (0, \b - \c/2) to node {$x$} (\c, \b - \c/2);
    \draw [<->] (\c, \b - \c/2) to node {$80 - 2x$} (\a - \c, \b - \c/2);

    \draw [<->] (-0.5, 0) to [xianduan={below=0.5cm}]  node [rotate=90] {$60$} (-0.5, \b);
    \draw [<->] (\c/2, 0) to node [rotate=90] {$x$} (\c/2, \c);
    \draw [<->] (\c/2, \c) to node [rotate=90] {$60 - 2x$} (\c/2, \b - \c);
\end{tikzpicture}
